Field
The present application relates to a device for detecting precipitation conditions and other meteorological conditions.
Description of the Related Art
Adverse precipitation conditions can have a significant negative impact on activities performed by individuals and organisations. One such adverse precipitation condition is freezing rain, which arises when liquid rain drops are supercooled as they fall, and subsequently freeze on contact with a surface, resulting in a coating of ice on the surface. Freezing rain can cause a wide range of problems, from increasing the risk of personal injury due to slipping or road traffic accidents, to dangerous build-up of ice on aircraft and damage to trees, roofs, power cables, pylons, wind turbines and other structures due to the weight of accumulated ice. Thus, prompt and reliable detection of freezing rain and other adverse weather conditions is required by national weather services, transportation, power and civil protection authorities.
Known methods for detecting ice involve either emitting or receiving near infra-red radiation for remote detection, continuous assessment of the resonant frequency of a protruding metallic probe, or detection of changes in the capacitance of an exposed surface.
Whilst all of these methods have been shown to work, all have disadvantages. For example, using near infra-red remote detection will only provide a yes/no result and not a quantitative estimation of ice thickness or accumulation rate. Additionally, near infra-red solutions require line of sight, meaning that any windows between the infra-red emitter and receiver will need to be clean and clear of contamination including drifting snow.
Resonant frequency probes typically offer a relatively small surface area for precipitation to adhere to, and so there is a reduced probability of correct detection of freezing rain during light rainfall. Additionally, the cost of such probes can be prohibitive.
Capacitance based sensors typically also offer only a yes/no result, rather than providing any quantitative estimation of ice thickness or accumulation rate, and may be vulnerable to contamination and erroneous results, as the detection technique involves estimation of relative permittivity. Such sensors are typically able to detect water accurately, as the relative permittivity of water is around 80 times that of air. In contrast, the relative permittivity of ice is much lower, at around 3 times that of air, and so detection of ice may be less accurate, as a surface layer of contaminants on the sensor having a similar relative permittivity value may be incorrectly identified as ice.
Thus, a need exists for an accurate, cost effective and reliable device for detecting freezing rain and other precipitation conditions.